#50: Giant Ancient Fish Fed Like Whales

In evolution, some ideas are so good that they come up again and again. Last year paleontologists in Britain and the United States learned that during the Cretaceous era huge fish drifted through the oceans with mouths agape, ingesting plankton through specialized filters, thus filling the ecological niche that humpbacks and other baleen whales occupy today.

Previously, scientists had found only a few fossils of filter-feeding fish, which lived about 145 million years ago and then seemingly went extinct. Large plankton eaters did not appear again until about 60 million years ago, when suspension-feeding sharks emerged.

That huge gap stumped researchers until last year’s discovery by University of Oxford paleontologist Matt Friedman, who identified a 15-foot-long fossil fish, previously excavated from a slab of rock in Kansas, as a filter feeder. Bonnerichthys, as he called it, dated to around 75 million years ago, long after such animals were thought to have vanished. Friedman subsequently reexamined dusty museum archives and found neglected fossils showing that similar gape-mouthed, plankton-eating fish had thrived all over the world for more than 100 million years. That abundance indicates the creatures “were far more than just a blip on the evolutionary radar,” Friedman says. “They were a hidden dynasty.”